close

Вход

Забыли?

вход по аккаунту

?

Патент USA US2127564

код для вставки
2,127,564
Patented Aug. 23, 1938
UNITED STATES PATENT OFFICE
ZINC AMMONiUM CHLORIDE FLUXES
Raymond J. Kepfer, Lakewood, Ohio, .assignor,
by meme assignments, to E. 1. du Pont de Ne
mours 8: Company, Wilmington, DeL, a cor
poration of Delaware
No Drawing. Application March 5, 1936,
Serial No. 67,306
1 Claim. (CL 148-26)
This invention relates to zinc ammonium chlo~
ride galvanizing ?uxes, and is particularly direct
ed to processes whereinv unsatisfactory zinc am
monium chloride galvanizing ?uxes are made
5 suitable for use with foaming agents by reducing
the amount of sulfates present as impurities.
In hot dip galvanizing, a bath of molten zinc
is covered with a ?ux.
As articles to be gal
vanized are lowered into the molten zinc bath they,
10 of course, first pass thru the ?ux where they are
cleaned and prepared for the reception of a metal
coating.
It has heretofore been the practice to employ
foaming agents such as giycerine, tallow, and soap
15 bark with the flux in order to produce a foam or
froth. Ordinarily the foaming agent and flux are
separately added, as required, to the zinc bath.
Sometimes the zinc ammonium chloride flux and
foaming agent in predetermined proportions are
20 simultaneously. added to a zinc bath either by
adding a mixture of flux and foaming agent‘di
rectly to the bath or by adding such a mixture to
a pre-wash from which the metal being treated
carries the flux and foaming agent to the bath.
The foam produced by means of foaming.
25
agents serves to entrap vapors and gases and to
retard the rate of volatilization of the flux. For
galvanizing operations of this type it is essential
that the foam be satisfactory in character and of
30 sufficient thickness.
Galvanizers have frequently been confronted
with the dii?cuity that, for no apparent reason, it
is sometimes extremely difficult or even impossible
to obtain a satisfactory foam. Sometimes by
35 using a great excess of foaming agent it was pos
sible to obtain a moderately satisfactory foam.
In most instances, the diiliculties were surmount
ed only by purchasing a new lot of zinc am‘
monium chloride ?ux which would not be so un
lieo. satisfactory.
I have found» that this hitherto unaccountable
behavior on the part of zinc ammonium chloride
fluxes is attributable to the presence therein of an
excess of sulfate.
When sulfates are present in
excess of about 2% SO: in zinc ammonium
chloride fluxes, it is di?lcult or impossible to
produce a satisfactory foam by the use of the
customary foaming agents even when such agents
are used in very large amounts. Without a satis
50 factory foam on the galvanizing bath, it is, of
course, impossible to proceed with the galvanizing
operations. It is also observed that when exces
sive amounts of sulfates are present in zinc am~
monium chloride ?uxes, there is excessive "fum
55 ing”. That is, the ammonium chloride in the flux
:iublin'ies, rapidly destroying the efficacy of the
an.
Apparently the deleterious sulfates which ren
der zinc ammonium chloride ?uxes unusable are
inadvertently introduced into the flux in the
course of manufacture or they are present be
cause the crude materials used are high in sul
fates.‘ The sulfates are present, variously, as
zinc sulfate, ammonium sulfate, lead sulfate, and
evencalcium sulfate. Inasmuch as it is the sul 10
fate radical which is deleterious, I have referred
herein to the sulfate content in terms of the per
centage of SO: found, in accordance with standard
practice.
To render usable zinc ammonium chloride ?uxes
‘which contain excessive amounts of sulfates, it is
only necessary to remove the sulfates in any de
sired manner. I have found it most satisfactory
to remove so much of the sulfate as is necessary
by adding an acid soluble barium salt, such as 20
barium chloride or barium carbonate, to the flux
while it is in dilute solution in the course of its
manufacture. The resulting barium sulfate may
be removed by decanting or filtering the solution.
Strangely enough, barium sulfate does not seem
to exercise the deleterious effects experienced
with most sulfates unless the barium sulfate is
present in amounts exceeding about 5% as S03.
If it is desired, therefore, to remove relatively
small amounts of sulfate from concentrated zinc "
ammonium chloride liquors, the soluble barium
salt may simply be added and the resulting
barium sulfate included in the product. Of
course, if this procedure is followed, great care
must be exercised lest too large an amount of
barium sulfate be present.
if the ?ux and foaming agent are to be added
to a galvanizing bath indirectly by using the flux
and foaming agent in a pre-dip, the excess of sul
fate may be removed by adding a soluble barium
salt to the pre-dip. Here again, care must be
exercised lest the barium sulfate content be too
great.
'
Zinc ammonium chloride fluxes superior to those
heretofore offered the trade may be prepared by 45
removing substantially all of the sulfate content.
If it is not expedient to remove all of the sul
fate, zinc ammonium chloride ?uxes of very high
quality may be prepared by treating the zinc
ammonium chloride ?uxes so that no more than
0
about 0.1% S03 is present. If it is found desirable
to remove still less of the sulfate, satisfactory zinc
ammonium chloride ?uxes comparable to the best
commercial ?uxes heretofore o?ered the trade
may be prepared by removing sulfate so that no 55
2 .
2,127,664
more than about 0.2% 80: remains. It is notv
preferred,_ however, to leave as much as 0.2% 80:
in the flux because with this highest permissible
S03 content, it is ordinarily necessary to add a lit-'
tle more foaming agent than would be required
with the ?uxes having a lower S03 content.
The following examples are given more fully to
explain the practice of my invention.
Example I
A commercial zinc ammonium chloride gal
vanizing ?ux found unacceptable to the trade
was analyzed and was found to contain 1.79%
of sulfates computed as S03. This ?ux contained
soap bark as a ‘foaming agent. When this flux
was tried on a galvanizing bath, a foam formed
very quickly, reaching a maximum thickness of
about two inches, and subsiding after about four
minutes. Using this ?ux, there was excessive
20 fuming. Following the teachings of this inven
tion, the sulfates were removed from the flux by
adding barium chloride to an aqueous solution
thereof. Using the sulfate-free zinc ammonium
' chloride ?ux, a foam blanket about four and a
25 half inches thick was obtained. This foam lasted
for about twenty four minutes, and there was
very little fuming.
Example II
Another
commercial
zinc ammonium chloride
30
?ux found unacceptable to the trade was analyzed
was obtained. Very little fuming was noted with.
the improved ?ux composition.
Example IV
A commercial zinc ammonium chloride flux
which contained 1.25% of soap bark as a foaming
agent was analyzed and ‘was treated to reduce the
sulfate content to about 0.2% computed as S03.
The ?ux was much improved, leading to the pro
duction of a foam which lasted for about six
minutes, and which was about one and one-half
inches thick. There was moderate fuming. This
?ux was made more acceptable by increasing the
soap bark content to 2.5% after which there was
obtained a foam three inches thick which lasted
for fourteen minutes. The fuming was consider 15
ably lighter. It will be observed that at the upper
limits of sulfate content speci?ed by my inven
tion, it is necessary to use a larger amount of
foaming agents to produce entirely satisfactory
results. The use of an excess of a foaming agent
is, of course, expensive and undesirable, and it
is generally preferable, therefore, to reduce the
sulfate content as much as possible.
Example V
25
A concentrated zinc ammonium chloride liquor
which contained sulfates equivalent to 0.5% B01
was treated with barium chloride. The zinc am
monium chloride was crystallized from the solu
tion andqremoved therefrom together with the 30
and was found to contain 0.36% of sulfate com
puted as S03. Testing this ?ux on a galvanizing
pot, a foam about one inch thick and which
barium sulfate. The flux thus produced was used
on a galvanizing pot and, after adding foaming
35 lasted for only about two minutes was obtained.
tained a foam about two and a half inches thick
Considerable fuming of the ?ux was observed,
tho it was not quite as bad as the original ?ux
mentioned in Example I. Following the procedure
of this invention, the sulfates were removed from
The flux
then led to the production of a foam which lasted
for about twenty two minutes and which was
about four and a half inches thick.
Example III
40 the flux by the use of barium chloride.
A zinc ammonium chloride ?ux which was
found unacceptable to the trade was analyzed
and was found to contain 0.41% of sulfates com
puted as S03. This unsatisfactory ?ux produced
a foam which lasted for about four minutes and
was about one inch thick. This flux contained
0.7% of glycerine as a foaming agent. To re
duce the content of sulfates in the flux, there was
added thereto a sulfate-free zinc ammonium
chloride flux which contained 0.7% of glycerine.
The sulfate-free flux was added in an amount
sufficient‘ to bring the sulfate content of the mix
ture down to 0.05% computed as S03. The re
sulting mixture was used as a flux on a galvaniz—
60 ing pot and a foam which lasted for thirteen
minutes and which was about four inches thick
agents in the customary amount, there was ob
which lasted for about fourteen minutes. There
was very little fuming. It is thus noted that bari
um sulfate equivalent to 0.5% S0: does not exer
cise the deleterious effects observed with equally
large amounts of other sulfates. If barium sul
fate be present in larger amounts, however, it 40
adversely affects the characteristics of the ?ux.
While I have shown a number of speci?c pro
cedures in the foregoing, it will readily be ap
parent that the sulfate content of zinc ammonium
chloride ?uxes may be reduced in varying
amounts and by various procedures without de
parting from the spirit of this invention.
I claim:
4.5v
In a process for the treatment of a zinc am
monium chloride galvanizing ?ux which contains
sulfates and hence is unsatisfactory by reason of
the poor foam produced when it is used with
foaming agents, the flux containing no more than
about 0.5% S03, the steps comprising treating
the flux with a soluble barium compound to con 55
vert the sulfate to barium sulfate so that when
used with foaming agents the ?ux will produce
foams of satisfactory thickness and character.
RAYMOND J. IQEPFER.
Документ
Категория
Без категории
Просмотров
0
Размер файла
312 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа